Unify YAML-LD & JSON-LD examples

[anatoly-scherbakov]

Why

Examples in the current spec document are very differently themed.

What

Convert all code examples into one unified theme throughout the whole specification.

Which theme might that be?

Proposing to use the theme of the specification itself. For instance, we can describe its title, the fact that it derives from JSON-LD, the fact that it uses YAML as its syntax, etc.

[gkellogg]

Looks like a good approach to me.